


An Excellent Mind for Science

by 1863



Category: Batman v Superman: Dawn of Justice, DC Extended Universe, Justice League (2017)
Genre: Extra Treat, Getting Together, Hand Jobs, Light Bondage, M/M, Sensory Overload
Language: English
Status: Completed
Published: 2019-02-21
Updated: 2019-02-21
Packaged: 2019-10-27 10:12:00
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 8,647
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17764808
Author URL: https://archiveofourown.org/users/1863/pseuds/1863
Summary: “From what I’ve read about you, Mr. Wayne, there’s nothing you wouldn’t try at least once.”





	An Excellent Mind for Science

**Author's Note:**

  * For [liodain](https://archiveofourown.org/users/liodain/gifts).



> You had too many prompts that were just too tempting! I hope you enjoy this treat. <3

He hadn’t meant to eavesdrop. Truly.

But Bruce was usually so reticent, his use of words just as efficient as everything else he seemed to do in his life – how he moved, how he fought, how he dealt with the team – that when Clark caught the faint sound of Bruce talking so freely, his super-hearing kicked in without him even thinking about it.

Besides, Alfred was the one who’d let him in and told him that Bruce was down in the cave.

“Go on downstairs, Master Kent,” he’d said. “He won’t mind.” Clark raised an eyebrow at that and Alfred bit back a smile. “Let me rephrase,” he amended. “He will most certainly mind, but tell him I sent you down regardless. And then ignore the inevitable glare.” 

So Clark started making his way down the long staircase that led to the cave. He’d only gone about a quarter of the way when he heard Bruce talking and then the super-hearing happened and now, he’s lurking on the stairs, eavesdropping on a conversation that he knows he has no business listening to. 

He’s vaguely surprised that Bruce isn’t alone. Surely Alfred would have told him if someone else was there? Clark briefly wonders if it’s Diana or someone else in the team, but quickly dismisses the idea. Bruce never sounded like this when he spoke to them – there was always a certain distance in his voice, a kind of deliberate, conscious control that Clark never really knew what to make of. Or else he did a toned down version of the playboy billionaire the rest of the world got to see, which he mostly seemed to do just to get a rise out of the team. But it only ever seemed to work on Clark – Diana and Victor just rolled their eyes and Barry was still too in awe of his admittedly stupendous wealth. Clark had thought that Arthur, at least, might say something, but apparently now that he’d seen what Bruce was actually capable of, he just found the whole Bruce Wayne act funny. But it _always_ worked on Clark, even if he rarely let himself show it. There was just something about the way Bruce looked at him sometimes, something Clark couldn’t pinpoint but still set his teeth on edge. In any case, Clark had always suspected it was just another method Bruce used to keep them all at a distance.

Still, after Steppenwolf, Bruce wasn’t exactly unfriendly or cold towards the team. But he certainly never sounded like this, either. Whoever he’s talking to now made Bruce’s voice lose that edge of polite neutrality, softening it, making it seem more – well, _real_. 

“I don’t even know why I keep you around,” Bruce is saying. There’s a quiet huff of laughter and Clark’s curiosity skyrockets. Who could be down there and making Bruce _laugh_? 

“Maybe it’s because you never actually say anything,” Bruce adds. “Makes a nice change of pace, anyway.”

There’s no more talking for a little while, just the sound of various metallic clanks and scrapes and the clack of a keyboard being typed on. Bruce must be working on something, Clark thinks, and then that thought really sinks in: Bruce is _working_ on something in the _cave_ , and actually allowing this person (who can make him laugh!) to watch him while he works. 

Clark hesitates. Whoever it was must be a good friend. Or possibly even more than a friend. Bruce wasn’t exactly the type of person who shared much about his personal life; Clark had no idea if he was seeing someone. But if he was, and Clark just barged in – 

Clark winces. There was no way that was going to end well.

He considers just continuing down the stairs, making enough noise that Bruce would know he’s coming, and then just do what he came here to do in the first place. Alfred had told him to go down, after all, so it wouldn’t be his fault if Bruce got mad at him for intruding. But Clark stays where he is, curiosity still rising and reporter’s senses tingling, and almost without meaning to – _almost_ – his X-ray vision switches on and then he’s looking through the walls and down into the cave below him. And what he sees is – 

Clark shuts off the vision immediately. What, he thinks blankly. Was that – ? No, it couldn’t have been. But it was. Wasn’t it?

He cautiously turns the vision back on, just to double-check, and – yes. Yes, it definitely was.

Bruce was talking to an extraordinarily detailed, life-sized hologram of a fully costumed Superman.

Clark stares. Bruce seems completely ease, relaxed in a way that Clark has never, ever seen him, tinkering with some kind of bat-gadget on the workbench and tossing the odd comment or question at the hologram, which never actually responds. He's even wearing a t-shirt and jeans – and yes, okay, the t-shirt alone probably cost more than everything Clark was wearing combined, but still. Aside from the batsuit, Clark had never seen him in anything less formal than a pristine dress shirt with the sleeves rolled up. Seeing Bruce in a t-shirt, no matter how expensive, was almost like seeing him naked. Not that Clark ever thought about that. Much. 

“Damn circuit,” Bruce is saying, frowning at the gadget on the bench. “I think it’s fried.” He sighs. “I wonder if I should ask Victor or Barry to take a look at it. What do you think, Superman?” 

Clark jumps a little, even though he knows Bruce isn’t actually talking to him. 

The hologram says nothing, face impassive as it floats in mid-air. 

Bruce glances at it, then suddenly sets his tools down. He rounds the bench until he's right in front of the hologram and for several long minutes, he simply stares up at it, the expression on his face completely unreadable. 

_What_ , Clark thinks, tightening his jaw. _What are you going to say to it that you can’t say to me?_

He knows it’s irrational to be angry at some non-corporeal simulation of himself but Clark can’t help it. It just isn’t – _Clark’s_ the one who Bruce worked with to save the world. Clark’s the one who came back from the dead to help him, the one who apologised for trying to kill him when he first came back, the one who tries so hard not to cross Bruce’s innumerable, unpredictable boundaries. And yet here’s this thing that wears his face who gets to see all the things that Clark is denied – Bruce at ease, Bruce being friendly. Bruce _laughing_. It was hardly fair.

And neither is spying on him, Clark thinks guiltily, looking away. He sighs and runs a hand through his hair. Not for the first time, he wonders why Bruce always had to make things so damn complicated. 

Clark starts heading down the stairs again, but this time makes his footsteps markedly heavier. Bruce stiffens immediately and Clark switches the X-ray vision off, dialling back his hearing too. Bruce knows he’s coming now; if there was something Bruce wanted to say to him he could say it to the real thing.

“Bruce?” he calls, when he gets close to the foot of the staircase. “Alfred said I could come down, is it okay if I – ”

He cuts off when the door slides open.

“Clark,” Bruce greets. 

He’s leaning against the workbench, holding something that looks vaguely like a screwdriver, looking up at the space where the Superman hologram used to be. Except now, it’s been replaced with a blown-up schematic of the gadget he’d been working on earlier. 

Clark surreptitiously studies his face but Bruce just looks – completely normal. There’s nothing, nothing at all, not in his face or his demeanour, that would indicate that he’d just been staring intently at a perfect hologram of Clark’s alter ego. Even his heartbeat is steady, Clark thinks with irritation. Bruce was always so damn _controlled_. 

“What can I do for you?” Bruce asks. Polite but distant. As per usual. 

_You can start by telling me why you built a hologram of me_ , Clark doesn’t say. _And then tell me why you talk to it more easily than you talk to me._

“I just wanted to give you a heads-up that I’ll be at the charity event tonight,” Clark says. “Perry put me on it.”

Bruce raises an eyebrow. 

“Demoted to the social pages, Clark? What did you do to piss him off?”

“I’m not sure,” Clark replies, raising an eyebrow of his own. “But it _might_ have something to do with my skipping work to help you take care of that slime-monster thing in the Gotham sewers a couple weeks ago.”

To Clark’s amazement, Bruce actually cracks a smile. A real one, even, if only a small one.

“Point taken,” Bruce says, inclining his head in acknowledgement. “But you didn’t have to come here to tell me that. You’ll get a Bruce Wayne soundbite if you need one.”

Clark shrugs.

“Consider it a professional courtesy. We haven’t been seen together outside of League business since – ” Clark falters a little. Doomsday, he thinks. Right before Doomsday, right before he – 

“Lex Luthor’s party,” Bruce says, smoothly filling in the blank.

Clark clears his throat. Bruce always did that so easily, always knew what to say and when to say it. It was a skill Clark envied.

“Right,” he says, after a pause. “Anyway, I just – didn’t want to surprise you, that’s all.”

“Really?”

Clark blinks. “Excuse me?”

“You don’t want to surprise me?” 

“I, uh – ” 

Bruce has ducked his head a little and is looking at Clark from under his eyelashes, a small, almost mocking smirk on his lips. He pushes off the workbench, a smooth fluid movement that draws attention to his hips, and walks right into Clark’s personal space.

“Are you _sure_ you don’t want to surprise me?” he asks, tilting his head to one side. 

For a second, Clark actually thinks he’s being serious. But then he sees the amusement in Bruce’s eyes, the languid tilt of his mouth, the subtle slouch to his shoulders. This isn’t Bruce, not anymore. 

“This isn’t funny,” Clark says, voice sharper than he really means it to be.

But Bruce – Bruce _Wayne_ – just grins.

“Consider it a professional courtesy,” he replies, parroting Clark’s words back at him. “I didn’t want you to be surprised tonight, either. I mean…” He trails off and gives Clark a once-over, just a quick look up and down. “You do know how Bruce Wayne behaves at these types of events, don’t you?”

Bruce sweeps his fingers over Clark’s stomach as he steps past him and heads upstairs, not waiting for a response.

“Yeah,” Clark says to the empty room, voice a little unsteady as the heat from Bruce’s fingers starts to fade away. “Unfortunately, I do.”

***

“And your name is?” 

Bruce looks at him with absolutely no recognition on his face, but a clear gleam of appreciation in his eyes. Clark resists the urge to straighten his tie and holds out a hand instead.

“Clark Kent,” he says. “Daily Planet. We’ve met before.”

“Have we? I find that hard to believe.” Bruce smiles and and takes his hand, holding on too long as he gives Clark another once-over. But this one is altogether different from the one he gave Clark earlier, in the cave – this one is much slower, a languid, openly appraising sweep from head to toe and back up again. “I’m sure I’d have remembered you.”

Clark clears his throat.

“It was some time ago.” 

“Oh, well, then,” Bruce says, accepting a couple of champagne flutes from a passing waiter. “That means we should catch up, right?”

He holds out one of the glasses. Clark can’t very well refuse; people are already starting to watch them, and some quite blatantly. Not that Clark can really blame anyone for looking. Bruce Wayne drew people’s gazes like a magnet, and tonight, he’d pulled out all the stops – expensive cologne, perfect hair, and a three-piece suit that had to be bespoke, it fit him so well. Clark didn’t know that much about tailoring, pretty much just buying whatever he found that fit, but Bruce’s clothing made him realise that his definition of “fit” was somewhat misguided. Bruce’s clothes sat on his impressive frame like they _belonged_ there – every cut and seam and button, every colour and pattern and accessory, all forming part of one cohesive whole that told anyone who looked at him exactly what Bruce wanted them to know: that he was very powerful, that he was very handsome, and that he was very, very rich. 

“Like what you see?” 

Clark blinks. He hadn’t realised that he’d been staring. He quickly takes a sip of his champagne to cover his embarrassment but Bruce steps closer – very close – and Clark almost chokes on his drink.

“No no, not like that,” Bruce says. He wraps his fingers around Clark’s hand on the champagne flute. “Here, let me show you.”

He lifts their joined hands until the glass is at Clark’s lips again.

“You need to go slow,” Bruce says. His voice is very quiet and his eyes are very intent. “It's always better that way.” Bruce licks his lips. “Take a sip.”

Clark does as he's told and Bruce smiles, but there’s something sharp about it, something heated. Clark has to swallow again, throat gone unexpectedly dry.

“Good,” Bruce says approvingly. He looks Clark in the eye as he takes a sip of his own champagne. “You need to savour it, Mr. Kent. How it feels on your tongue. Inside your mouth. The flavour and the texture of it.”

Bruce holds his gaze and Clark finds himself unable to break it. He isn’t sure what Bruce is doing but the memory of how Bruce had spoken to his hologram overlays the way he’s talking to Clark now and abruptly, he feels irrationally angry all over again. All this time, he's done his best to be professional. At the end of the day, Clark knows that he and Bruce are on the same side, knows that Bruce has over twenty years of experience backing up everything he does as Batman. Clark trusts Bruce with his life when they’re on a mission, but in everyday life, right here, right now? Putting up with this Bruce Wayne bullshit when he’s just seen what Bruce could _actually_ be like – relaxed, open, _laughing_ – is one step too far. 

“You mean like this?” Clark asks, and takes another slow sip. He rolls the champagne in his mouth for a moment before he swallows, then slowly runs his tongue over his bottom lip, pretending to catch a stray drop that doesn’t actually exist. 

Bruce narrows his eyes and Clark smiles, feeling oddly triumphant. Two could play at this game.

“You learn fast, Mr. Kent,” he says, inclining his head just enough that Clark knows he’s talking about more than one thing. 

“Oh, Mr. Wayne,” Clark murmurs. “You have no idea.”

Something sparks in Bruce’s eyes then, a sudden flare of interest that’s never been directed Clark’s way before. 

“That sounds like an invitation, Mr. Kent.” Bruce smiles. “Or a challenge.”

Clark shrugs, then gives Bruce a once-over of his own. The suit didn’t quite show off just how dangerous the body beneath it was, but it certainly didn’t hide the fact that Bruce was six-foot-four of hard, sculpted muscle. He meets Bruce’s eyes again, and this time, there’s definite heat darkening the blue.

“Why not both?” he asks.

And Bruce – Bruce _smiles_. Not Bruce Wayne, but _Bruce_ , actual Bruce, and Clark’s heart is suddenly thumping in his chest as something electric seems to pass between them – some unspoken acknowledgement that now, it’s _on_.

Bruce opens his mouth and Clark braces himself, but they’re interrupted when a tall, strikingly beautiful woman appears at Bruce’s shoulder, wearing a dress that seemed to defy all laws of gravity.

“Brucie! How have you been?” 

In an instant, the look on Bruce’s face morphs from sharp, focused interest to a vapidly pleasant smile. The transition is so fast that Clark is disoriented for a second and doesn’t notice that he’s been asked a question until Bruce raises an expectant eyebrow.

“I’m sorry,” Clark says. “I didn’t quite catch that?”

“I asked whether you were new to Gotham,” the woman says. She gives him a once-over that would give even Bruce a run for his money. “I don’t recall seeing you at an event before. I’m Alice, by the way,” she adds. She holds out a hand – palm down, like she expects – what? For Clark to kiss it? Gotham was so weird.

“Clark Kent,” he replies, and gives her hand a firm shake. She looks a little put out but Bruce seems amused.

“He’s a reporter for the Daily Planet,” Bruce says. “From Metropolis.” 

“Metropolis, really?” Alice looks at him with renewed interest. “The home of the Superman?” 

“I’m... not really sure where he lives,” Clark says, a little taken aback. 

“But you do know him? You’ve seen him?” Alice leans forward and lowers her voice. “Tell me, is he really as perfect as the photos make him seem?”

“I’m not – not sure what you mean,” Clark says.

“Oh, come now, Mr. Kent,” Bruce says. A hint of the sharpness is back in his eyes as he very briefly lowers his gaze to Clark’s crotch. “You can tell us. _Is_ Superman a perfect specimen of the male form?” He laughs a little, a low rumble that Clark seems to feel in places that really shouldn’t be feeling anything right now. “His costume doesn’t exactly hide anything.”

Clark clears his throat.

“Well, he’s an alien,” he says. His voice is only a little rougher than it should be but Bruce, of course, notices it anyway. “Who knows what’s under the costume, really.”

“True,” Alice says. “But don’t tell me either of you wouldn’t ride that six ways from Sunday given half a chance.” 

She and Bruce laugh, but Bruce’s eyes stay fixed on Clark the entire time. 

Alice leaves soon afterwards, called away by someone she describes as “an utter bore” and who Bruce later informs him is her husband. Clark doesn’t feel too badly for her. They probably deserved each other, he thinks uncharitably, thinking of the way she practically wrapped herself around Bruce’s side.

“So, Mr. Wayne,” Clark says, when they’re alone again. He hesitates, but only briefly. “ _Would_ you ride that six ways from Sunday?”

Bruce turns to face him. There’s a certain hardness in his eyes now and for a moment, Clark wonders if he’s overstepped the mark, or worse, completely misread the situation. But then Bruce steps closer, not so close that it’s inappropriate but enough to make it clear that yes, Clark had definitely read the situation correctly. 

“That depends,” Bruce says softly, “on what’s under the costume.” 

His voice is so low, so deep, that it’s almost at modulated Batman levels, but much, much smoother – just a few rough catches here and there that make Clark’s mouth go dry and his heart pound hard in his chest. He’s never heard Bruce sound like this, never, and if this is what it does to him then it’s probably just as well. Clark had never really thought about Bruce’s voice before, but now that it’s focused on something other than chairing League meetings or giving orders in the field, Clark is rapidly starting to wonder if maybe, just maybe, he’s gotten in a little over his head. 

But Bruce isn’t exactly unaffected either, Clark realises. His eyes are darker than usual, and even if his heartbeat is still infuriatingly steady, he’s looking at Clark with an expression that’s almost… hungry. Clark takes a deep breath and – yes, under the cologne, under the soap and skin and shampoo, there’s the unmistakable scent of arousal, too. 

Clark tips his head back, the challenge clear in his eyes.

“Would you be willing to find out?”

Bruce raises an eyebrow.

“Experiment, you mean?”

“Why not?” Clark shrugs. “From what I’ve read about you, Mr. Wayne, there’s nothing you wouldn’t try at least once.”

“You shouldn’t believe everything you read, son,” Bruce replies, lips curling into a small, knowing smile. “But on that particular point, you probably _can_ believe it.” He pauses for a moment, then gives Clark a speculative look. “I do wonder, though,” he adds, “whether the same could be said about him.”

Clark frowns. “What do you mean?”

“Well, if I’m willing to experiment,” Bruce says, “I don’t think it’s unreasonable to ask that he does, too.”

Bruce’s eyes are hotter than ever now and Clark distantly wonders if this is how people feel when he turns on his heat vision. He resists the urge to loosen his tie but Bruce smiles suddenly, like he knows exactly what Clark is thinking, and Clark takes another sip of champagne to stall for time.

“What did you have in mind?” he asks eventually.

And as soon as he says it, he knows he’s made a mistake. Bruce’s smile widens and he takes a step closer, crowding Clark against the wall before he leans one hand against it, effectively trapping him. There is definitely nothing appropriate about how close they’re standing now but Bruce doesn’t seem to care. 

“Kryptonite,” Bruce says. Clark freezes. “I’ve heard it has a bad effect on him. But perhaps a more… judicious use of it, could have some benefit. In certain situations.”

Clark licks his lips. He doesn’t miss the way Bruce tracks the movement of his tongue.

“A small amount,” he starts, but his throat is so dry that he has to stop and try again. “A small amount could… make things interesting. Maybe.”

Bruce stares at his mouth for a moment before lifting his gaze and looking him in the eye.

“Interesting?” he repeats.

Clark nods. 

“It could allow you to – ” Clark takes a breath, but he’s come too far to back down now. “To experiment,” he continues. “With whatever’s under the costume.” 

Bruce gives him a long, searching look. There’s still unmistakable hunger and heat in his eyes, but Clark can also see him running the numbers – doing the calculations, assessing all the risks. And then something flickers over his face, like a shadow of some deeply buried thing that Clark doesn't understand but for some reason almost makes him want to call the whole thing off. But then Bruce lowers his head and takes a deep breath, and when he looks at Clark again there’s a smile on his face and something almost predatory in his eyes. Clark feels his face heat up and Bruce’s smile widens. 

“Mr. Kent,” he says, in the same quiet, intense voice he’d used earlier, the one that Clark has never heard him use with anyone else before. “That sounds like an _excellent_ way to spend an evening.”

***

The piece of kryptonite is tiny – just a chip, really, not any bigger than a small jewel you’d find on a cheap ring. But Clark still feels its effects, all over and inside his entire body, and even inside his own head, too: an unfamiliar heaviness in his bones that his fuzzy mind identifies as weakness. When Clark tugs a little at the ropes around his wrists and ankles, he knows he won’t be able to pull himself free. 

Rope, he thinks. Reinforced chains couldn’t stop him if he was at full power, but Bruce chose to go with rope.

“Hemp rope,” Bruce had corrected him. “It’s the traditional material for this sort of thing.”

This sort of thing being _bondage_ , Clark thinks, and resists a wild urge to laugh. Of course Bruce just happened to have some hemp rope lying around. Of course he knew how to use it. Of course Clark has somehow ended up willingly bound by it, trussed up and spreadeagled on a large metal frame somewhere in the depths of Bruce’s cave. Things always seemed to get a little out of control for Clark wherever Bruce was concerned.

They’re both still fully clothed, although Clark is down to shirtsleeves and slacks, his jacket tossed into a corner. Bruce, however, still looks immaculate – he hasn’t even taken his cufflinks or collar bar off, nor loosened his tie. 

“I’ll just leave this here,” Bruce says now, setting the kryptonite on a desk not far from where Clark is tied up. It’s in a small box lined with lead, and Bruce keeps the lid flipped open to allow the the radiation to spread throughout the room. 

“You have more than that,” Clark says. It’s not a question, and Bruce doesn’t treat it as one.

“This is all I need right now,” he says instead. His gaze runs all over Clark’s bound body, a long, thorough stare that almost makes Clark squirm. “Judicious use, right?” Bruce adds, voice notably deeper than it was a second ago.

“Right,” Clark manages.

Bruce steps closer. 

“Is it affecting you now?”

Clark nods. “Yes.” 

“How?”

“I – ” Clark licks his lips. “I can’t get free.”

Bruce seems pleased by that. “Show me.”

Clark tugs at the bond on his left wrist, pulling as hard as he can. The metal frame rattles loudly but the knot holds firm. He can feel the rough scrape of it against the soft skin of his inner wrist; can smell the strange, earthy scent of it, and it makes him a little dizzy. He wonders who else Bruce has used it on, who else he tied up with such swift, practiced skill. He wonders if Bruce had looked at them the way Bruce is looking at him now: dark-eyed and approving, a small sharp smile just barely curving his lips. 

“Good,” Bruce says. “Very good.”

Then he reaches out and starts unbuttoning Clark’s shirt.

“Uh,” Clark says.

Bruce glances at him but doesn’t stop.

“Now now, Clark,” he says. “You’re the one who suggested an experiment.” He pauses when the shirt is undone, tugging it open to reveal Clark’s bare chest. Almost as an afterthought, he unbuttons Clark’s waistband too. “So far,” Bruce says, “so human. In appearance, at least.” 

He tilts his head to the side, blatantly looking over every curve and dip of muscle, watching with sharp interest as Clark’s chest rises and falls more rapidly the longer he keeps on staring. 

“But looks can be deceiving, can’t they?” Bruce asks. His voice is very quiet. “I think we need to test for responses to various stimuli.”

“What,” Clark starts, and has to pause to clear his throat. “What kinds of stimuli?”

Bruce’s smile widens. 

“Why don’t we start with something simple?” 

And he reaches out and runs a fingertip down Clark’s bare chest. He traces the edge of a pectoral muscle, slowly circling in closer and closer to the nipple until Clark is practically arching off the frame. But Bruce bypasses it entirely and just drags his finger to the other side of Clark’s chest, repeating the motion at the same torturously slow, steady pace.

“Bruce,” Clark starts, but then the finger sweeps lower, down over his stomach, skimming across his abs, before it starts following the line of hair that disappears into the waistband of his slacks. Clark forgets what he was going say, biting his lip and closing his eyes, shifting restlessly as Bruce’s warm, calloused finger keeps sliding down, down, down – 

And stops.

Clark eyes flicker open and he gasps in surprise – he’s looking directly into Bruce’s eyes, their faces barely an inch apart. Bruce’s pupils are blown wide but it’s the only indication of how this is affecting him – Clark’s hearing isn’t as good as it could be, not with the kryptonite in the room, but it’s still good enough to know that Bruce’s heartbeat is as steady as ever. Clark wishes he could say the same about his own, but the flush on his skin and the growing bulge in his pants make it pretty clear how he’s feeling anyway. 

Without breaking eye contact Bruce drags his finger lower, over Clark’s slacks, and traces the line of Clark’s rapidly hardening cock.

“Oh,” Clark breathes, hips jerking a little. Bruce smiles, and Clark’s eyes are immediately drawn to his mouth. Bruce’s touch becomes firmer, pressing down over the length of him as Bruce parts his lips a little. Then the tip of his tongue emerges, slowly sweeping over his bottom lip at the exact same pace as his finger moves over Clark’s cock. 

_“You need to savour it, Mr. Kent,”_ Bruce had said, earlier that night. _“How it feels on your tongue. Inside your mouth. The flavour and the texture of it.”_

Clark leans forward without even meaning to and immediately, Bruce takes a step back.

“What – ” Clark pants. His head feels scrambled, body overstimulated and yet not nearly stimulated enough, and Clark gets a sinking feeling that it’s as much because of Bruce as it is the eerie green glow at the edges of his vision.

“A finger seems to yield excellent results,” Bruce murmurs. “But I think it’s time to test the next stimulus.” 

“What – ” Clark repeats. It seems to be all he’s capable of saying at the moment. He shakes his head, trying in vain to clear it. “What is it?” 

Bruce leans forward, mouth hovering just out of reach. 

“I've been wondering,” he whispers against Clark’s lips, “how you taste, Mr Kent.”

Then he bends his head and licks a slow, wet stripe up the side of Clark’s neck. 

“ _God_ ,” Clark gasps, surprised, head instinctively tilting to give Bruce better access. 

“Hmm.” Bruce licks his lips, a thoughtful expression on his face. 

“Well?” Clarks asks.

“I think I need a bigger sample size.”

Bruce looks him dead in the eye and smiles. And then he sinks to his knees.

“Jesus,” Clark whispers, staring as Bruce licks his lips again.

Clark hadn't expected this – he hadn't known _what_ to expect, really, but the image of Bruce kneeling had never been one that he’d been able to picture clearly. Oh, he’s certainly tried – many times, lying in bed on restless nights when Metropolis was unusually quiet, or standing under the hot spray of a shower after a mission with the team. But he’d never been able to really _see_ it. Not Bruce, who was so physically imposing even out of the batsuit, who was always so frustratingly, infuriatingly in control. And yet here he is now, Clark thinks, staring down at him, willingly putting himself in a position like this. A position of – of _service_ , Clark realises, and has to swallow as heat floods his veins at the very thought.

But Clark should have known that Bruce, of all people, could bend any situation to his own advantage. Even when he was on his knees. 

Bruce leans forward and pulls the zipper of Clark’s slacks down with his teeth. 

Clark just stares, wide eyed and panting. Bruce briefly meets his eyes before he presses his tongue against Clark’s cock and Clark can't help himself, can't control his reaction to this at all – the sight of Bruce on his knees below him, the feeling of Bruce's tongue tasting him through the thin fabric of his underwear. His hips thrust hard, a tiny sound of need escaping his throat, and when Bruce pulls back and laughs, low and dark and amused, Clark’s cock goes from semi-hard to all the way there in about half a second flat.

“Do you,” Clark starts, voice embarrassingly hoarse, “have enough data yet? Or do you need – ” Clark licks his lips. “Another taste?”

Bruce looks up at him through his eyelashes. The pose might be coquettish but there's absolutely nothing innocent about the expression in his eyes. Bruce looks like he's contemplating every possible way that he could _ruin_ Clark, and even if Clark didn't already know how Bruce's mind worked – that he was thorough and meticulous and very, very patient when he needed to be – Clark is so far gone already that he'd let Bruce try out every single one of them anyway. The kryptonite in his system might be lowering his inhibitions as well as his strength, but it was nothing compared to the sight of Bruce on his knees, or the new-found knowledge of how Bruce’s tongue felt, pressed hard against him.

“I think I do, yes,” Bruce says, after a long, heavy pause. “If something’s worth doing,” he adds, “it's worth doing well.”

Then he leans forward and starts mouthing at Clark’s cock. 

“ _Fuck_ ,” Clark chokes, trying desperately to keep still. It doesn’t work very well but Bruce doesn't hold him back, just keeps moving his head to make sure Clark never gets more than what Bruce wants him to have, and making sure his mouth is the only point of contact between them. Clark tries to get his breathing under control but it’s no use; every brush of lips and every flick of tongue seemingly designed to make him go mad. Bruce sucks lightly on the tip, tongue swirling around the head, lips sliding firmly along the whole hard length of him and even through the fabric Clark can feel how warm his mouth is; can tell that Bruce is as good at this as he is at seemingly everything else. Then Bruce looks up at him, heat in his eyes and mouth still on his cock, and something tightens in Clark’s chest, a sudden hit from out of nowhere that makes him shudder hard all over.

“ _Bruce_ ,” he moans, unable to keep it in any longer. It bursts out of him, almost painful, and then – 

Without any warning, Bruce pulls away again. He's panting now, just a little, his lips red and swollen and Clark can finally see it, he can imagine it all so clearly – that mouth stretched wide around his bare cock, taking him in all the way; his hands tight in that salt-and-pepper hair as Bruce’s head moved between his legs.

“God, Bruce,” Clark whispers hoarsely, staring at Bruce’s parted lips. “Your _mouth_ – ”

And Bruce is suddenly standing, leaning in as close as he can while still keeping just out of Clark’s reach. 

“Tell me,” he says, in a voice no less commanding for being very, very quiet. “Tell me what you want me to do with it.”

“I – I – ” Clark stammers. 

It's hard to think clearly, not with Bruce standing so close, not with the kryptonite still soaking into his bones. And then Bruce bends his head and licks roughly at a nipple and Clark’s brain shudders to a complete halt, thoughts melting into a puddle of wordless pleas for more, yes, _please_. Bruce keeps licking, and sucking, and biting hard – hard enough that Clark actually feels it, feels the hot stab of pain, a sensation so unfamiliar that it takes him a second to recognise it for what it is. And by then it's too late – he's already cried out, eyes shut tight; already arched his back and given away that he doesn’t just like it – he wants it to hurt _more_. 

Bruce lifts his head. Clark forces his eyes open, shame burning his face, fully expecting to see Bruce laughing at him.

Bruce isn’t laughing. He’s not even smiling.

“ _Clark_ ,” he says. 

His voice is hoarse, ragged with something that makes Clark hot all over, and through the haze of kryptonite and lust Clark realises that the thundering in his ears isn't just his own blood rushing through his veins anymore – it's Bruce's too, heart finally pounding just as fast as his own. 

For a long, heated moment, they just stare at each other, both of them panting and painfully hard. Bruce's erection looks obscene against the otherwise pristine lines of his perfectly tailored suit but the contradiction just makes Clark that much harder. There's a terrifying heat in Bruce's eyes, something almost wild and barely in control – like maybe he hadn't expected things would go this far; that maybe, like Clark, he thinks he’s in way over his head. But then Bruce smiles, wide and feral, all teeth, and grabs Clark by the hair. His fingers tighten, painfully hard, and Clark gasps, cock twitching at the sensation. Bruce yanks Clark’s head to the side and whispers roughly into his ear. 

“I think it's time to test one last stimulus.”

Then he abruptly steps away. 

Clark can’t even respond, his thoughts too jumbled, his body too weak to fight it. He hangs limply on the frame, head bowed, and wonders if this is what being drunk feels like – and if it is, whether that means he’s drunk on Bruce. 

A faint _click_ makes him look up. The world seems to snap into focus as he watches Bruce come closer again. He’s got something in his hands, and as Clark’s head slowly starts to clear something hot curls in his belly, some half-formed idea of what Bruce is doing starting to take shape in his mind. 

Bruce opens the box again. Only for a second, just to show Clark the kryptonite, and before it starts to make Clark woozy again Bruce quickly snaps it shut. He presses a finger against what must be a biometric lock, and then – 

He hurls the box to other end of the cave. 

It lands with a dull thunk. Clark just stares at him, still not entirely sure what Bruce is trying to do. With the kryptonite shut away everything suddenly seems sharper, colours more vivid and shapes more defined, Bruce's face so clear it almost hurt to look at it. 

“What are you – ”

“I want your head clear for this,” Bruce interrupts. He stalks closer. The wild light in his eyes has faded a little, pulled back into a tightly coiled spring – still there, but kept in check through sheer force of will. If anything it just makes Clark harder, the knowledge that Bruce is capable of controlling even _this_ – and the knowledge that that control could break at any moment. 

“My strength,” Clark starts. “It will come back.”

“I know.”

“Do you – ” Clark has to swallow against the dryness of his throat. “Do you want me to pull free?”

Bruce steps closer. He leans in, lips barely brushing Clark’s jaw. 

“Do you want to pull free?”

And this, Clark realises, as his body gets stronger and his mind starts to clear, this isn’t just a question – it’s a test. Whatever he says now will shape the course of more than this one night, Clark is sure of it. And he’s equally sure of what answer he wants to give.

He turns his head, just enough to see Bruce's face. Bruce's eyes are still on him, watching, waiting, mouth so tantalisingly close. All Clark had to do was lean in. 

“No,” Clark says. 

“No?”

“I don't want to pull free.”

Something lights up in the depths of Bruce's eyes, a sudden flare of heat and surprise and – approval. It makes Clark flush, his cock twitch, and with effort he turns his head away from the terrible temptation of Bruce's perfect mouth. 

Bruce rewards his restraint by leaning in close again. 

“Last stimulus,” he whispers into Clark’s ear. One of his hands lands on Clark’s chest and the other on Clark’s back, before both of them drift lower and lower. Clark has to strain to keep still, because now Bruce is slowly pulling his underwear down, just far enough to expose his leaking cock.

“Open your senses, Clark,” Bruce says softly. “All of them.”

Clark tries to protest but Bruce suddenly grabs his cock, giving it a slow firm stroke and Clark promptly chokes on whatever it was he was going to say. 

“Open your senses,” Bruce repeats. 

His hand is still moving, but _slowly_ , agonisingly so, inch by maddening inch. 

“God, _Bruce_ ,” Clark moans, helplessly thrusting into Bruce’s fist, head falling forward and chest heaving with the effort of not yanking himself free. Bruce's hand is warm and calloused and strong, and it knows exactly what it's doing. 

“Clark,” Bruce says, a note of warning in his voice. 

“I can't,” Clark whispers desperately. “This – you – it's already too much, I _can't_ – ”

“Yes, you can.” Bruce's voice is so quiet, so deep, so intent. 

“I can't – ”

“You _can_.”

Bruce's thumb circles the head of his cock as he leans in even closer, so close that when he speaks again Clark can feel his breath hot against his skin, lips brushing over the shell of his ear. “Do you know how I know that?”

“How,” Clark pants, hands balling into fists as he forces himself not to pull free. Bruce is so _close_ , close enough to kiss, close enough to touch – 

“Because I asked you to." 

Another slow stroke, another swirl of his thumb in just the right spot, and Clark shudders hard, gasping. And just when he starts to wonder how long this will last, how much more of this he could possibly take, Bruce steps around and presses _right_ up against his back, hand still stroking all the while.

“Fuck, _Bruce_ ,” Clark moans out, pushing back against him, desperate to feel the whole long length of Bruce’s body behind him, broad and strong and utterly unyielding.

Bruce’s cock is hard and hot against his ass as Bruce starts rubbing against him and Clark bites his lip so hard he might have torn it off if the kryptonite were still in his system. It feels so _good_ , better than anything he's imagined, and the knowledge that it could feel even better – that Bruce could do this without the barrier of their clothing, that Bruce could speed up his hand, that Bruce might have wanted to do that and more this entire time – 

“Open your senses, Clark,” Bruce repeats, the roughness of his voice in Clark’s ear as unbearably good as his hand on Clark’s cock. “I want you to _feel_ this,” Bruce says, tightening his grip, “in every way you can.”

And Bruce's voice is so softly persuasive, his breath so warm and reassuring against the back of Clark’s neck, that Clark starts letting the barriers fall without him really thinking it through. 

Sights and sounds and smells start bleeding in; a trickle at first, and then a flood: the thrum of Bruce's heartbeat roaring in his ears; the rough drag of Bruce's fingers as they move over his cock; the unmistakable scent of Bruce's arousal. It's almost violent in its intensity, overwhelming in a way that Clark has rarely experienced, every one of his senses turned all the way up to eleven. All he can smell is Bruce, so strong he can almost taste it – the salty tang of his skin, the bitterness of his pre-come, the musk and wood of his cologne. Clark feels himself losing control, senses opening up more and more, and now he can hear Bruce's heavy breaths pushing in and out of his lungs, he can feel every single beat of Bruce’s heart pounding against his back where Bruce is still pressed up hard against him. And the hand on cock – 

“Oh _fuck,_ fuck, _Bruce_ – ” Clark whimpers, as Bruce starts stroking faster, fist tightening, spreading pre-come as he goes. 

Every stroke sparks a pleasure so intense it’s almost painful, a searing white hot burst that Clark feels _everywhere_ , all over and all at once – over his skin, up his spine, inside his own _head_. He's barely aware of the noises he's making, desperate breathless moans pulled from somewhere deep in his chest; tiny wordless sobs ripped from somewhere even deeper. He thinks he says Bruce's name, cries it out as Bruce starts rocking his hips, his cock pressed hard against Clark’s bare ass, and this too Clark feels with searing clarity, bone-deep and overwhelming. 

It makes it all too easy to imagine how this would feel if Bruce were doing it without his suit in the way, and easy to imagine how it would feel if Bruce was even _closer_ – Bruce pushing into him, the whole hot hard length of him, driving in deeper and deeper, thrusting harder and harder, knowing he could fuck Clark as hard as he wanted and not even leave a bruise. And all once it becomes too much, the cacophony of sensations pushing Clark to his absolute limit. Bruce is everywhere; the taste of him on his tongue, the scent of him in his lungs, the heat of his skin burning him even through the layers of their clothing. It's like the kryptonite but somehow even worse, or better – Clark can't tell the difference anymore, not with Bruce's hand flying over his cock, not with Bruce panting harshly into his neck, and definitely not when Bruce’s erection finds the cleft of his ass and pushes in hard. 

“Fuck, please, _Bruce_ ,” Clark begs. His arms and legs start to shake, still desperately trying not to pull himself free, and then Bruce grabs his hair and pulls his head back against his shoulder and almost, _almost_ kisses him. 

“ _Clark_ ,” Bruce pants against his mouth, voice rough and raw, face flushed and looking more undone than Clark has ever seen him. He pulls Clark even closer, rubbing himself against Clark’s ass like he doesn’t know how to stop, like he can't even control himself, and more than anything it's this, the realisation that he's broken through Bruce's ironclad self-control that does it – Clark comes with a choked-off shout, mind whiting out, whole body shuddering and blind to everything except the solid warmth of Bruce at his back, Bruce's fingers wrapped around him, Bruce's wrecked voice moaning his name. 

***

Clark is still panting and weak-kneed when Bruce steps away from him. The loss of contact is disorienting and Clark has to force himself to focus when Bruce steps around to face him. 

“You,” Bruce says, voice deeper than Clark has ever heard it, “you came. But you're still hard.”

“So are you,” Clark replies, eyeing Bruce's crotch. Bruce hasn't come yet but there's a wet patch at the front of his slacks, fabric probably worth more than Clark’s entire rent stretched taut over his very obvious erection. Clark licks his lips. With effort, he lifts his gaze. 

Bruce is still watching him. Aside from that one damp patch, at first glance he still looks immaculate – tie and collar bar still perfectly straight and snug against his throat, shirt and cuffs and vest buttoned up all the way. But Clark can see things clearly now, and not just because the kryptonite has been locked away. He runs his eyes all over Bruce, drinking in all the details now that he knows he's allowed to look, and sees all the tiny fractures in Bruce's surface-level composure: the dark gleam of something fierce in his eyes, the rapid rise and fall of his chest, the tiny knowing curl of his lips. Bruce isn't as in control as he seems, and he's letting Clark see it. 

“Looks like we're not quite done, then,” Clark says. His own voice surprises him, much deeper and rougher than he expected, but if the way Bruce's pulse picks up it can only be a good thing.

“How long will it last?” Bruce asks, looking at Clark’s cock with something very much like greed.

“I'm not sure,” Clark replies. “I haven't really tested it.” He stares at Bruce’s mouth. “I think I'd need appropriate stimuli for that. You know, for science.”

“Well,” Bruce says, the ghost of a smile on his face and the spark of a challenge in his eyes. “If it's for science – ”

Clark is pretty sure he breaks the frame – and a chair, and possibly a shelving unit or two – as he literally flies out of his restraints, but he doesn’t let that slow him down for a second. Besides, he thinks, as his lips finally make contact with Bruce's smirking mouth, it's not like Bruce can’t afford to replace them. 

***

It's nearly a month later, when he's idly wandering around the cave while Bruce is hunched over a laptop, that Clark remembers to ask about it. 

“So,” he says, as casually as he can manage. “Hologram?”

Bruce’s back stiffens. 

“You know about it,” Bruce says. It's not a question. 

“Yes,” Clark replies, but something about Bruce’s voice suddenly makes him feel a little apprehensive. “It was the day of the charity event – ”

Bruce turns his head and meets Clark’s eyes.

“You were spying on me?”

“What? No, I – ” Clark looks away. “Yes,” he admits. “But it was an accident,” he adds quickly, a sudden panic spreading in his chest at the thought that maybe he’d gone too far, that Bruce would see this as a violation and not just a stupid mistake. “I didn't mean to, Bruce, I swear – ”

Clark stops. Stops and stares, because Bruce is – Bruce is _laughing_. Just a quiet sort of chuckle, but still definitely a laugh. He's laughing in the cave, while he worked, with Clark at his side. 

Just like he’d laughed with the hologram that day.

“Calm down, Clark. It’s not a big deal.”

“It's not?”

Bruce shrugs. “I built it to run simulations. Fight simulations, before – ”

He stops suddenly, the break into silence so sharp that Clark can almost feel it, like a crack in the air. Bruce isn't laughing anymore, his face darkened by memories that Clark knows he'll never allow to fade, no matter how often Clark tells him that it's okay, that it's in the past, that he's forgiven. Bruce looks away, like he knows what Clark is thinking and doesn't deserve even that much. 

“Before the team got together?” Clark asks, keeping his voice even, finishing the abandoned sentence for him. 

Bruce goes still, so still he's stopped breathing – Clark knows, because he hears it stop. It seems like a very long time before Bruce sucks in a breath, a sharp inhale that seems to punctuate some internal decision he's just made. He turns to face Clark fully, swivelling in his seat, legs spread wide as he comes to a stop.

“Yes,” Bruce says. His voice is very quiet. “But I guess I don't need it anymore. Not for fight simulations, at least.”

Then he looks up at Clark and just – waits. 

Clark thinks carefully before he replies, searching Bruce's eyes, trying to understand what Bruce is trying to tell him. Everything Bruce did had a thought behind it, a specific purpose that led to a specific result. And right now Bruce is in the cave with him, as unguarded as Clark has ever seen him, sprawled in a chair with his legs spread and – 

Inviting, Clark realises. Inviting, and waiting, and maybe... maybe hoping, too.

Clark steps forward. His fingertips brush over Bruce's thighs as he fits himself into the space between Bruce's legs with improbable ease. 

Bruce lowers his head and takes a deep, deep breath. He stays like that for a minute, deep in thought, and when he looks up again his face hasn't really changed – except for the smile in his eyes that he’s put there specifically for Clark to see.

“Then again,” Bruce says, after a pause, “maybe I should keep it. Use it to test…” He trails off, lips curling into a tiny smirk. “Other kinds of simulations, maybe.” 

“You could,” Clark agrees, pressing in closer, closer, until Bruce takes the hint and grabs hold of his hips. “Or you could just run your tests on the real thing.” Clark touches his face, brushes a lock of hair off his forehead. "I mean, your data would be more accurate that way."

“Have you ever considered a career change?” Bruce asks. His hands travel upward and tighten around Clark’s waist, and if it's not quite a promise, at the very least it's a start.

“No,” Clark says. “Why?” 

He leans down and smiles when Bruce reaches up, pulling him down further. 

“Because you have an excellent mind for science, Mr. Kent.”


End file.
